This disclosure is a method for SO2 recoveries from sulfur plants to reduce the sulfur emissions. The present invention is combinations of modifications of the prior arts which produces sulfur and other SO2 and H2S and the present invention is added to adsorbs the SO2 that is produced in the prior arts in other words to reduce SO2 emission by adsorbing the SO2 that is produced in the prior arts. The prior arts is required to be modified, optimized, resulting adding piping, equipment, catalysts and instrumentation where the present invention is added after the prior arts is qualified for the implementation. The present invention is as a supplement unit or polisher unit that serves only the prior arts in sulfur recovery and tail gas treating units.
The present disclosure is added to the prior arts of the sulfur technologies to reduce SO2 emission. As the results the prior arts is modified or optimized to achieve a better results with combinations of prior arts and the present invention overall 100% recovery is or zero SO2 emission is achieved. Therefore, since the prior arts generate a tail gas stream where is considered as the feed gas to the present invention; the description of prior arts are discussed in this application; considering the performance of prior arts has direct impacts on the present invention. The prior arts is modified and upgraded to have a more efficient performance as well as for the purpose of receiving a recycle stream from the present invention.
This disclosure relates generally to Process the remaining un-recovered SO2 from the prior arts in sulfur plant by innovative ADSORBENT/REGENERATION Process and by using two SO2 adsorbers consists of adsorbent catalysts. The Present Invention consists of 2 major vessels where they are switching between the adsorption and desorption or regeneration mode and they are located after the tail gas incineration and before the stack replacing of any other supplement unit similar to the caustic absorber system.
The adsorption mode operates at cold temperature to adsorb the SO2. The regenerator mode operates at hot temperature to regenerate the SO2 by adding a slip stream of the H2S acid gas stream and a slip stream of the air from the SRU air blower to the top of the adsorber that contains adsorbed SO2. The adsorbers consist of the adsorbents catalysts; H2S to react with the adsorbed SO2 in the vessel with oxygen present and the gas stream leaving the regenerator or hot adsorber is then recycled to a sulfur plant as a new stream to the prior arts of thermal section or downstream of the prior arts of Claus thermal section. The gas stream from the cold adsorber flows to the stack and it is SO2 free and zero emission is achieved.
In summary, the present invention comprises adsorption and desorption steps for recovering SO2 and H2S from a tail gas stream as a flue gas from the prior arts that is incinerated wherein, in the present invention first SO2 is adsorbed in a fixed bed adsorber and then desorbed by a regeneration gas which comprises a portion of the acid gas feed that generally flows to the prior art of a sulfur plant and returning the regeneration gas as the recycle to the prior arts of a sulfur plant. The sweeping gas flows the regenerator adsorber with a portion of the combustion air that normally fed to a prior art sulfur plant to remove the remaining of the un-recovered SO2 and H2S and returning the recovered SO2 and H2S to the prior arts sulfur plant. It means the prior arts sends a portion of its feed to the present invention, instead receives a new stream from the present invention that contains SO2 and H2S.
step 1) providing a flue gas stream from an prior art incineration unit into present invention two identical fixed bed adsorbers, one of said adsorber operating in a cool adsorption mode and the second adsorber operating in a hot regeneration mode, where each adsorber is capable of a cycle wherein the adsorbers operate in a hot mode and a cool mode, and the modes can alternate and during the cool mode the adsorber operates as an adsorbent and the in the hot mode the adsorber operates as a regenerator; step 2) when operating as a regenerator, said fixed bed adsorber comprises adsorbent catalysts used inside of each identical vessel; step 3) when operating as an adsorbent, said fixed bed adsorber receives a cooled incinerated flue gas outlet stream for the adsorption of SO2 from the prior arts tail gas stream; step 4) when said fixed bed adsorber operates in a regenerative mode or hot mode, providing a amine acid gas slip stream and an air slip stream from the prior arts into said adsorber to regenerate adsorbed SO2; step 5) said the present invention process further comprises control devices and motor operated switching valves to control the adsorber to enable switching or alternate modes between adsorption modes and regeneration modes to provide an outlet streams one stream being free of sulfur to be vented to the stack and a second stream comprising a the recovered sulfur components to be recycled to a prior art sulfur recovery unit; step 6) said outlet gas stream when the adsorber is operated in the adsorption mode produces sulfur-free flue gas which is vented or introduced to a stack; and the outlet gas stream when the adsorber operates in the regenerative mode is recycled back to a prior art sulfur plant or downstream prior art of a tail gas treating unit or injected to the thermal section of a Claus unit that includes a reaction furnace, or to the catalytic stages of a Claus unit that includes Claus reactors or Claus condensers and to a tail gas treating unit that includes tail gas hydrogenation reactor; and wherein, said process reduces the SO2 emissions from 50 ppmv to less than 10 ppmv.
The adsorbent catalysts are made specially shaped to perform efficiently from Alumina, promoted Alumina or titanium or combination materials in a form of adsorbent located in the adsorbers.